In Gulliver's Travels, a 21st century twist on Jonathan Swift's enduring political satire, Jack Black plays a travel writer who gets sucked into the Bermuda Triangle and winds up on the miniaturized island of Liliput. As you could imagine, vfx played a vital role in this Rob Letterman-directed film from Twentieth Century Fox. Weta Digital, Scanline VFX, Hydraulx, Method Studios, Pixel Playground and India-based GEON and Tata were the primary vendors that contributed to the 600 shots.

According to Ellen Somers, the overall vfx supervisor during post (Jim Rygiel served the same function during production), Weta and Scanline took on significant water simulation sequences; Hydraulx created the Liliput CG environments and two robot sequences; and Method did a 2.5D rooftop sequence gaining the reality from the base of photographic images. She also singled out GEON's exemplary compositing and suggested they are definitely on the rise.

"The biggest challenge was the scale issue involving a guy that's 126-feet tall," Somers points out. "What kind of vaporization happens when he hits the water? Working all that out was important and getting near what's scientifically correct and making it look good. The big sequences, which are pretty impressive, I think, are the whirlpool at the head of the film and the storm sequences by Scanline, and Weta's work on the sequence where Gulliver has to vanquish the army made up of Liliputians. This is heady R&D stuff where you wish you had 26 weeks to do it and they only had about 11. Weta rescheduled their whole facility and gave us their entire effects team."

Indeed, Weta came onto the project late, and, as the workload grew in complexity, the New Zealand studio's role increased from a few shots to around 170. "We did the scene where Gulliver first appears on the beach where the Liliputians are all over him; we did the scene where he is wearing the exo-suit where he's being controlled like a big marionette; we did the scene in the middle where Gulliver dispatches an armada of ships (the biggest because of water interaction); and the Times Square scene (laid out by Hydraulx) with Gulliver-based advertising," explains Weta's supervisor, Guy Williams.

"We built on the water sim for Avatar, but had to push it a lot further because it needed to be a lot more convincing, large-scale water," Williams explains. "It required a lot more density to the voxels and a lot more particles for foam and things like that just to get the sense that he's 120-feet tall. We further developed a tool called Synapse that allows you to stitch together simulations from different vectors and merge them into one simulation. This meant that we could merge the wave sim together with a high-density fluid sim and then that could be merged with the high-density fluid sim for the wakes on the boat and the foam could be emitted from that one unified sim.

"We continued our collaboration with the guys at Exotic Matter using Naiad (their dynamic solver and simulation framework) whenever we hit a wall. So a lot of the fluid simulation was actually done through Naiad and then used our own hooks to do things like aerations based off the density in the water and used our own tools to put the foam and the sort of white water rack on top.

We came up with the ability to turn the foam into millions of little particles and then spread out so it would look like particular mist, which really helped it look like giant water."

In terms of the Times Square scene, Hydraulx made the CG buildings but Weta added more detail through their own texturing and weathering system. And using Weta's image-based lighting system and spherical harmonics provided quick turnaround.

"Another thing we've added to our pipeline since Avatar is that we not only have indirect [lighting] but also three bounces of indirect," Williams adds. "And, where light bounces around, you'll actually get highlights on streets or into windows from the indirect component, not just the direct light sources, which give you a realistic lighting feel, which meant that you could lay out the lights in a proper way. We lit these shots as if they were live-action sets. We hit pin caves behind buildings shining up on top of buildings; and we did volumetric god rays so it felt like it was a back lot shot."

Meanwhile, for the Bermuda Triangle storm, full CG environments, including water, atmospherics and 3D, 2.5D and 2D skies were created by Scanline (under the supervision of Bryan Grill and Stephan Trojansky). Plates of Gulliver in his boat were shot in London, using a full-scale, partial boat on a gimbal and practical water dump tanks for direct interaction. The job of extracting Gulliver and his boat, the Knotfersail, and immersing them into the storm of the century, fell to Compositing Supervisor Chris Ledoux and his team. However, for some shots, all elements, including the boat and Gulliver, were fully digital.

As Gulliver gets tossed around in the growing storm, we are introduced to a towering water funnel, violently spinning counter-clockwise and spewing spray and foam. The water funnel was the result of an extensive design and development process, during which it evolved from a more conventional funnel emerging from the sky, into an inverted whirlpool of churning, stormy water that towers over Gulliver and the Knotfersail, eventually sucking him up and into a water funnel that transports him to Lilliput. The task of both design and execution, aided by the latest advances in Scanline's proprietary Flowline software (for which the company received a 2008 Sci-Tech Academy award), fell to CG Supervisor Danielle Plantec and Flowline artist Masakazu Murakami, along with a development team spearheaded by Trojansky.

In addition, Rok!t Studio created the imaginative title sequence. Rok!t shot the sequence in stereo in six days at a very slow frame rate to create an erratic motion in the New York City plates. When back in the studio, Rok!t applied a tilt-shift process, which gives the shots a miniaturized look so that all of the boats, buildings and vehicles tend to look like small models. Rok!t also built the 3D CG main titles which were composited into the scenes of the city. For the end titles, they designed an animated newspaper sequence of Gulliver's published travel column, which carries the drawings and end credits. Locations include Times Square, Liberty Park, Governor's Island, an aerial of Central Park, Top of the Rock and Columbus Circle.

Lee Nelson, Rok!t vfx supervisor, proposed doing the title sequence in stereo when it was first suggested that it be converted like the rest of the film. Testing with two digital SLRs and a very simple rig provided good results, and the director approved the method. "We shot half the sequence with these Canon 1D Mark IV SLR digital cameras with my little rig that syncs the shutters, and the other half with the Genesis cameras using a beam splitter," Nelson explains.

However, he was unable to shoot above Central Park because of President Obama's presence there, so they shot around the park and then stitched together the aerial perspective in the computer using a stereoscopic rig in Maya, Nuke, After Effects and Silhouette for roto.

"Stereo, to me, when you shoot it, is the same sensation as shooting still photography," Nelson adds. "You don't appreciate it until you get it back into your box and you're looking at this beautiful high-res imagery in 3-D."